U.S. patent number 5,259,459 [Application Number 07/695,634] was granted by the patent office on 1993-11-09 for subsea wellhead tieback connector.
This patent grant is currently assigned to FMC Corporation. Invention is credited to William A. Valka.
United States Patent |
5,259,459 |
Valka |
November 9, 1993 |
Subsea wellhead tieback connector
Abstract
A subsea wellhead tieback connector actuated solely by axial
motion to achieve connection to and disconnection from the
wellhead. The connector includes interconnected inner and outer
bodies, a split lock ring surrounding the inner body, and an
energizing mandrel for non-rotary axial movement to expand the lock
ring into engagement with a wellhead component.
Inventors: |
Valka; William A. (Spring,
TX) |
Assignee: |
FMC Corporation (Chicago,
IL)
|
Family
ID: |
24793820 |
Appl.
No.: |
07/695,634 |
Filed: |
May 3, 1991 |
Current U.S.
Class: |
166/345; 166/237;
166/217; 166/359; 285/123.4 |
Current CPC
Class: |
F16L
37/12 (20130101); E21B 33/043 (20130101); E21B
33/038 (20130101) |
Current International
Class: |
F16L
37/12 (20060101); F16L 37/00 (20060101); E21B
33/043 (20060101); E21B 33/03 (20060101); E21B
33/038 (20060101); E21B 023/00 () |
Field of
Search: |
;166/341,344,345,348,382,217,237,359 ;285/18,24,39,141,920 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1197680 |
|
Jul 1970 |
|
GB |
|
2111625 |
|
Jul 1983 |
|
GB |
|
2162919 |
|
Feb 1986 |
|
GB |
|
2165908 |
|
Apr 1986 |
|
GB |
|
Primary Examiner: Britts; Ramon S.
Assistant Examiner: Schoeppel; Roger J.
Attorney, Agent or Firm: Cruz; Lawrence Megley; Richard
B.
Claims
What is claimed is:
1. A tieback connector for use in connecting a riser, conductor or
other well pipe to a subsea wellhead, said connector
comprising:
(a) a tubular outer body with a bore, an upper end, a lower end
surface, and a plurality of axial slots in said bore;
(b) means for attaching the outer body to a well pipe;
(c) a tubular inner body;
(d) means for interconnecting the inner and outer bodies;
(e) a split lock ring surrounding the inner body beneath the lower
end surface of the outer body;
(f) an annular lock ring energizing mandrel between the inner and
outer bodies for axial non-rotary movement between upper and lower
positions to expand the lock ring into locking engagement with a
wellhead component and thereby connect the tieback connector to
said component; and
(g) means for rotating the inner body with respect to the outer
body causing axial movement of the inner body in order to establish
a preload on the lock ring when the lock ring is in locking
engagement.
2. A tieback connector according to claim 1 wherein the inner body
has a lower outer axial surface, an upper outer axial surface of
less diameter than said lower surface, and an upwardly-facing
annular shoulder formed by a generally radial surface extending
between said lower and upper surfaces.
3. A tieback connector according to claim 2 wherein the inner body
radial surface and upper outer axial surface cooperate with the
lower end surface of the outer body to form an annular recess
within which the lock ring resides in contracted position.
4. A tieback connector according to claim 1 wherein the energizing
mandrel comprises a continuous body portion and a plurality of
elongated fingers extending downwardly from said body portion and
within the outer body slots.
5. A tieback connector according to claim 4 wherein the elongated
fingers are spaced circumferentially with respect to the mandrel
body portion and terminate in tapered lower ends.
6. A tieback connector according to claim 1 wherein downward axial
movement of the mandrel causes the mandrel fingers to expand the
lock ring into its functional locking engagement with the wellhead
component.
7. A tieback connector according to claim 1 wherein the mandrel
includes means for connecting it to a well tool to actuate the
mandrel in an axial non-rotary direction.
8. A tieback connector according to claim 1 wherein the inner body
includes means for connecting a well tool to said inner body for
adjusting the relative axial positions of the inner and outer
bodies.
9. A tieback connector according to claim 1 wherein the means for
interconnecting the inner and outer bodies comprises threads.
Description
BACKGROUND OF THE INVENTION
This invention relates to subsea well equipment, and more
particularly to equipment, referred to as tieback connectors, used
to interconnect well conductor or riser pipe with a wellhead
beneath the water surface.
For many years the petroleum industry has been producing oil and
gas from offshore wells wherein the wellhead is located underwater,
i.e. subsea, and the Christmas tree is positioned on a platform or
other surface facility. Extending between these subsea wellheads
and their surface trees are relatively large diameter conductor or
riser pipes that are attached to the wellhead housings by tieback
connectors that require rotation of a pipe string to lock them to,
and release them from, the housings. Although right-hand rotation
of the pipe string during the locking procedure usually presents no
problem, when the string is rotated to the left to unlock the
connector the joints in the string can unthread, and reconnecting
those joints presents a serious and costly problem to the
operator.
SUMMARY OF THE INVENTION
The present invention solves the foregoing problem by providing a
tieback connector that is actuated by axial motion to achieve
proper connection to, and disconnection from, a wellhead. No rotary
motion is required for these operations, and therefore the danger
of drill pipe unthreading is eliminated.
A tieback connector according to the present invention comprises a
tubular outer body with means, such as threads, for attaching it to
a pipe string, a tubular inner body within and connected to the
outer body, an axially split lock ring surrounding the inner body
beneath the lower end of the outer body, and an annular energizing
mandrel between the inner and outer bodies to expand the lock ring
from an inherently contracted position into an annular groove
system in the wellhead housing or other component with which the
tieback connection is to be made. The energizing mandrel has a
continuous body portion from which downwardly extend a plurality of
circumferentially spaced elongated fingers that reside in internal
axial slots in the outer body bore, the fingers terminating above
the lock ring when the mandrel is in its upper or "unlocked"
position, and residing behind the expanded ring when in its lower
or "locked" position to hold the ring in functional position in the
housing groove system. The connection between the inner and outer
bodies of the connector facilitates assembly and, if needed,
position adjustment of the connector components, and an optional
axial slot in the bore of the inner body enables rotation of that
body with respect to the other connector components to apply a load
on the ring after it has been expanded into functional locking
position.
Further features and advantages of the present invention will
become apparent from the following description in combination with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary central section through a tieback connector
according to the present invention, showing the connector landed in
the upper end portion of a wellhead housing and ready for actuation
from its unlocked to its locked condition.
FIG. 2 is a view like FIG. 1, showing the tieback connector locked
into the wellhead housing.
FIG. 3 is a fragmentary isometric view of the unlocked connector
and housing of FIG. 1, showing the energizing mandrel fingers in
their axial slots in the outer body of the connector.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As illustrated in the drawings, a tieback connector 10 according to
the present invention comprises a tubular outer body 12, a tubular
inner body 14 connected to the outer body 12 such as by threads 16
or other suitable means, a split lock ring 18 surrounding the inner
body 14 below the lower end surface 20 of the outer body 12, and an
energizing mandrel 22 having an upper annular body portion 24 and a
plurality of circumferentially spaced elongated fingers 26
extending downwardly from the body 24 in axial slots 28 in the bore
of the outer body 12.
The outer body 12 has an external annular downwardly-facing
shoulder 30 and a frusto-conical surface 32 that seat on
complementary surfaces 34, 36, respectively, on a wellhead housing
38 when the connector 10 is properly landed on the housing, and
annular seals 40 provide a pressure-tight seal between the outer
body 12 and housing 38. The inner body 14 has an upwardly-facing
annular shoulder 42 between its lower outer surface 44 and its
upper reduced diameter surface 46, and this shoulder 42, the
surface 46 and the outer body lower end surface 20 cooperatively
form an annular recess in which the lock ring 18 resides (FIG. 1).
The inner body 14 carries an outer annular seal 48 for sealing the
body to the interior surface 50 of the wellhead housing 38, and
ratch-a-latch grooves 52 in its bore for connection to an inner
casing element 54.
The body 24 of the energizing mandrel 22 has an inwardly oriented
annular flange 56 for connecting the mandrel to a tool (not shown)
to axially move the mandrel between its upper and lower positions
as shown in FIGS. 1 and 2, respectively, and the mandrel is
retained in the outer body 12 by a snap ring 58. The lower ends of
the mandrel fingers 26 are tapered at 60 to facilitate their
passage behind the lock ring 18 as the mandrel is moved downward to
expand the lock ring from its "unlocked" or contracted position
shown in FIG. 1, into its "locked" or expanded position as seen in
FIG. 2.
The lock ring 18 has an outer surface profile complementary with a
groove profile in the internal surface 50 of the wellhead housing
38, such as the grooves 62 as seen in FIGS. 1 and 2. Thus when the
ring 18 is expanded into two of the grooves 62 (FIG. 2) it
effectively prevents the tieback connector 10 from moving upward
with respect to the housing 38, thereby locking the connector to
the housing.
By adjusting the axial spacing between the inner body radial
surface 42 and the upper frusto-conical surfaces 62a-c of the
grooves 62, a pre-load can be imposed through the ring and onto the
connector, such adjusting being accomplished by means of the
threads 16 interconnecting the inner and outer bodies 14, 12. If
pre-load adjustment is needed or desired after the connector has
been run, an axial slot 64 can be included in the bore of the inner
body 14 to provide a means for connecting a tool (not shown) to
rotate the inner body with respect to the outer body 12, thereby
causing axial movement of the inner body surface 42.
Although the best mode contemplated for carrying out the present
invention has been herein shown and described, it will be apparent
that modification and variation may be made without departing from
what is regarded to be the subject matter of the invention.
* * * * *